It sometimes becomes necessary to control the gain of a circuit or device as a function of another circuit parameter. In copending U.S. Pat. No. 4,228,323 issued to Feiner, et al on Oct. 14, 1980, there is disclosed a circuit for gain control of an optocoupled circuit using a DC voltage to control the AC gain of the circuit. In the Feiner patent, a DC reference voltage is used and is compared to the DC component of the control voltage and the error between the compared voltages is used to modify the AC gain of the circuit. The technique, while effective to accomplish the desired result, uses a multiplication circuit and operational amplifiers. Such components are costly and not easily integratable into a high density substrate. Thus, it is desirable to design a circuit for gain control using the DC component of the signal, but to do so with circuitry which is economically incorporable into integrated circuit technology.